1) Interleukin-4(IL-4) and its soluble receptor are being tested in the clinic for rheumatoid arthritis, asthma, and cancer by systematic injection or by gene transfer using viral vectors. Studies are underway to characterize structure, function, signal transduction and targeting of IL- 4 expressed on immune and cancer cells. The structure and function of receptor for IL-13, another IL-4 related interleukin, is also being investigated. Reconstitution studies have demonstrated that IL-13R' chain is a novel component of IL-4R in non-hematopoietic cells and the common IL-2R chain is a component of IL-4R systems in hematopoietic cells. It is also demonstrated that IL-4R chain is a necessary component of IL-13r system. Thus, IL-4R and IL-13R share more than one chain with each other. These studies help explain the mechanism of efficacy and toxicity seen when unusually low concentrations of IL-4 are used in cancer patients. 2) To understand the molecular mechanism of signal transduction by the IL-4 AND IL-13 receptor, we have studied the phosphorylation and activation of JAK kinases and signal transduction activator of transcription (STAT) intracellular proteins. Our studies demonstrate that both IL-4 and IL-13 utilize similar tyrosine kinases and same STAT6 for signalling in cancer cells and this pattern is different from immune cells. IL-4 can utilize either IL-13R' or IL-2R chain with IL-4R chain for its signal transduction. IL-13 also utilizes IL-4R and IL-13R' chain for signal transduction. These studies explain why IL-4 and IL-13 have redundant effect on a variety of cell types. Additional reconstitution experiments are underway to examine which kinases associate with various chains of IL- 4 and IL-13R complexes. 3) The IL-4 and IL-13R directed targeting of a Pseudomonas exotoxin, Diphtheria toxin, or alternatively receptor directed gene transfer is also being investigated. The receptors for these two interleukins are expressed in abundance on human tumor cells that offer an attractive target for toxin therapy for gene therapy. In vivo experiments in nude mice using human brain tumor has demonstrated complete responses in 100% of the animals in response to circular permuted IL-4 toxin. Pre- clinical experiments including pharmokinetics and toxicology in mice, intracerebral administration in rats and intrathecal and i.v. administration in monkeys have been performed. Based on these results, our phase 1 clinical trial was approved by CBER. We have treated one patient at John Wayne Cancer Institute, Santa Monica, CA at the lowest dose with no evidence of toxicity. Additional patients are being enrolled. These clinical studies will help elucidate safety profile of this and other chimeric toxins in clinic under various INDs.